Method for separating spot welded panels



April 27, 1965 E. D. HouGEN l 3,180,018

METHOD FOR SEPARATING SPOT WELDED PANELS Original Filed Dec. 5. 1960 7 f i sa 4s 2a 19a Vzz, f (e7 ,a

F'fa INVENTOA EvERs'r-r D. Hausen BY M4@ MKM United States Patent O 3,130,018 METHUD FUR SEPARATNG SPT WELDED PANELS Everett li). Heiligen, PA). Box 174, Flushing, Mich. @riginal application Dec. 5, 1960, Ser. No. 73,590, now

Patent No. 3,104,564, dated Sept. 24, 1963. Divided and this application Apr. 1, 1963, Ser. No. 269,349

Claims. (Cl. 29-40'1) This invention relates generally to metal working methods and more particularly to a method of disconnecting and rejoining metallic members which are originally joined together by one or more spot welds.

This application is a division of applicants co-pending application Serial No. 73,590, iiled December 5, 1960, now Patent No. 3,104,564, granted September 24, 1963, coveriny apparatus for separating spot welded panels.

ln the art of repairing and relinishing collision damaged sheet metal parts of automotive Vehicles, such as the body panels and fenders thereof, it is often necessary to remove the damaged panel from the vehicle in order to straighten 'or otherwise recondition the same. When the sheet metal panels are joined together by spot welds, the damaged panel has hitherto been separated from the undamaged panel either by drilling a hole of sutlicient diameter through both panels so that the entire spot welded portions of the panels are removed, or by splitting the spot-welded seam apart by driving a thin sharp chisel between the two panels.

Both methods have disadvantages. In the former, it is necessary to center punch the spot weld in order to properly position and start the drill in true position. Drilling out the entire spot welded portions of both panels consumes excessive time and power, and it is practically impossible to make overlapping drillings when tworspot welds are` located close together. Moreover, in rejoining the repaired panel to the undamaged panel, the presence of holes in both of these panels requires the use of sophisticated, high temperature welding tools and techniques often unavailable in the average body shop. in the chisel method of separating the panels, the undamaged as well as damaged panels are often distorted and bent, adding to the labor and cost involved in making the repair.

Accordingly, it is an object of the present invention to provide an improved method for separating two metallic members joined by a spot weld in which a minimum of metal is removed without distorting the members, thereby reducing the time, power and expense required to effect the separation.

Another object is to provide an improved method for quickly cutting apart and rejoining sheet metal pieces which are connected by spot Welded portions, which method facilitates accurate re-alignrnent of the members during re-assembly thereof and which employs low temperature rewelding or brazing tools and techniques available at low cost and easily mastered by body shop personnel.

in the accompanying drawing:

HG. 1 is a perspective view of a rotary cutting tool used in practicing the invention.

HG. 2 is a longitudinal section of the rotary cutting tool taken on line 2--2 of FlG. l.

FIG. 3 is a fragmentary elevational View, partially in section, illustrating the step in the method of the invention for separating two panels spot welded together, utilizing the tool illustrated in FIGS. 1 and 2.

FlG. 4 is a fragmentary elevational View partially in section illustrating the completion of the step shown in FIG. 3.

FIG. 5 is a fragmentary sectional view of the panels 3,l.80,0l8 Patented Apr. 27, 1965 disconnected from 'one another and with the tool removed.

FlG. 6 is a fragmentary elevational view of a portion of the overlapping spot welded seam along which the panels are joined together, with encircling grooves cut around two of the spot welds thereof.

FIG. 7 is a fragmentary elevational view in section of the two panels re-assembled in accordance with the method of the invention.

FIG. 8 is a fragmentary elevational view of a modified form of tool usable in practicing the invention.

The rotary cutting tool 1t! (FIGS. 1 and 2) used in practicing the invention includes a cylindrical body or arbor 11 which is adapted to be received in suitable tool holding means of a rotary power supplying device, such as a chuck C of an electric hand drill, not otherwise shown. The forward end portion of arbor 11 is providedy with external threads 12 which mate with internal threads .1d of a double-ended cylindrical cutter blade 16 removably` received on the end of the arbor.

Cutter blade 16 is made in the form of a sleeve withV a plurality of cutting teeth 17 and 18 formed inV the respective peripheral end edges thereof. Cutting teeth 17 and 13 are shaped for high speed metal cutting in accordance with known design, but are reversed with respect to one another so that cutter blade 16 is reversible, thus permitting cutting teeth 18 to be used after cutting teeth 17 have become dulled from use. The central portion of cutter blade 16 is provided with an integral flange 19 which provides radial shoulders 19a and 19b spaced axially inward from cutting teeth 17 and 18 respectively, this spacing being determined by the maximum penetration for which the cutter blade 19 is designed.

Arbor 11 has an axial bore 21 formed in the forward portion thereof which opens into a counterbore to be cut. The rear end of rod 24 is upset to form any enlarged portion 27 which abuts shoulder 23 to limit forward travel of pilot rod 24.

Pilot rod 24 is urged to a fully extended position (FIG. 2) by means of a resilient member comprising helical compression spring 2.8 slidably received in counterbore 22. The rear. end of spring 28 abuts an externally threaded plug 29 threadably received in internal threads 311 provided at the rear of counterbore 22. Plug 29 is provided with a transverse slot 29a adapted to receive a screw driver for usein axially adjusting the plug. A bearing ball 32 rides with a rolling, sliding fit in counterbore 22 between the forward end of spring 28 and enlarged portion 27 of pilot rod 24 to form an anti-friction seat therefor. Rearward travel of bearing ball 32, and hence pilot rod 24, is positively limited by the provision of a spacer rod 33 slidably received within spring 2S. Spacer rod 33 is cut to a predetermined length so that when plug 29 is adjusted axially to the rear of arbor 11, the conical point 26 of pilot rod 24 may retract ush with the forward end of arbor 11 (dotted line showing,

which pilot rod 26 can move during retraction thereof before it is stopped by bearing ball 32 bottoming against rod 33 and the latter bottoming against plug 29.

A modified form of depth gauge is shown in FIG. 8. In this embodiment, there is no projection provided on spacer rod 33 and arbor 11 need not be slotted. Instead, a gauge plug 36 is provided in lieu of plug 29. Plug 36 has an externally threaded portion 37 adapted to be received in the internal threads 31 of counterbore 22. Integral with threaded portion 37 and extending rearwardly therefrom is an Unthreaded cylindrical portion 3S which projects beyond the end of arbor 11 [and terminates with a screw driver slot 39. Suitable gradiations 41 are provided on the outer surface of portion 38 to visibly indicate the axial position of plug 36.

To set the depth of penetration of cutting teeth 17, either form of tool is brought up against the surface of the portion of the Work to be cut so that point 26 of pilot rod 24 is retracted flush with the leading edges of cutting teeth 17. Plugs 29 or 36 are then screwed axially into arbor 11 until pilot rod 24, bearing ball 32 and spacer rod 33 abut one another. Plugs 29 or 35 are then rotated in the reverse direction to move the same axially rearward a distance equal to the depth of cut desired. This distance is easily read by observing the registry of gradiations 11b with projection 33a, of the gradiations 41 with respect to the rear face of arbor 11. Of course, cutting tool 10 may be constructed without depth gauging structures such as projection 33a and extension 38, in which case the depth of penetration may be set rather @accurately by observing the axial position of plug 29 and performing one or two test cuts, depending upon the skill of the operator.

The operation of rotary cutting tool 10 will become more apparent in the following description of the method of the invention for disconnecting and rejoining two metallic members spot welded together. Referring first to FIG. 3, a pair of sheet metal panels 42 and 43 are shown joined together by a spot Welded portion 44 thereof. The thickness of the panel to be removed is determined, and the screw plug 29 of the rotary cutting tool 10 is adjusted to penetrate at least all the way through this panel. With tool 10 thus adjusted, it is brought perpendicular to the surface of panel 42 with the conical point 26 against the center of the spot welded portion 44. Tool 10 is then pushed lightly against the panel, causing the pilot rod 24 to retract against the force of spring 28 until cutting teeth 17 contact panel 43. Due to the anti-friction bearing ball 32, pilot rod 24 is free to remain fixed against rotation when rotary motion is imparted to the cutting tool simultaneously with the application of the cutting teeth to the panel.

As shown in FIGS. 4 through 6, upon applicaion of moderate pressure, cutting teeth 17 penetrate panel 42 (and preferably a short distance into panel 42), cutting an annular groove 45 around the periphery of the spot welded portion 44 of the panels. Further penetration of cutting teeth 17 is prevented by pilot rod 26, since further retraction of the pilot rod is prevented by the abutment of the rear face of enlarged portion 27 against bearing ball 32, which in turn, is held against further axial movement by spacer rod 33 bottoming on the forward face of plug 29.

After the cut is completed, the rotary cutting tool is withdrawn and panels 42, 43 separated from one another, as shown in FIG. 5. A circular hole 43a is formed in outer panel 43, while the spot welded portion of panel 43 which remained in the center of the annular cut forms a cylindrical projection 43b on the surface of inner panel 42 since it is still welded thereto. Separation of the panels is made possible by the circular cut around .the spot welded portion 44, since the panels are joined together only at the spot Welded portion and not at other adjacent portions of the overlapping seam. It is to be understood that the outside diameter of cutter blade 16 measured at cutting teeth 17 must be equal to or larger than the diameter of the spot welded portion 44 to effect separation of the panels. It has been found preferable to use a rotary cutting tool having an arbor of one quarter inch outside diameter so as to tit the quarter inch electric drill found in most body shops, and having a cutter blade with an outside diameter of 5/16 inch so as to encircle most spot welds found on present day cars and trucks. However, if a variation in the diameter of spot welds is encountered, it is a simple matter to change to a cutter blade with a diameter large enough to encircle the spot weld.

After the disconnected panels have been straightened or otherwise reconditioned, they may be easily r'e-assembled in accordance with further steps in the method of the invention. As shown in FIG. 7, panels 42 and 43 are re-aligned with one another in the original connected arrangement thereof merely by relocating projection 43b in hole 43a. After all the projections are thus centered in the respective holes from which they were cut, the panels are temporarily held together by a clamp or other suitable means. Low temperature tools (welding or brazing) are then used to heat the panels around the groove 45 and low melting point welding metal 46 is puddled therein to fuse with and form a bond between the side walls of hole 43a, the surfaces of projection 43b and the bottom of the groove. The freshly cut annular groove 45 simplifies the rewelding of the panels since it provides a well for the molten metal and furnishes a clean, bright metal area for a high strength, low temperature bond.

The rotary cutting tool illustrated is also useful in cutting straight-through holes in metal, such use being shown in FIG. 8. -For this type of work, pilot rod 24 is adjusted for full retraction (flush with the forward end face of arbor 11) to permit maximum penetration of cutter blade 16. After the combined thicknesses of the panels 42 and 43 are penetrated, the point 26 will forcibly expel the disk-like portion 47 cut from the panels. Further penetration of cutter blade 16 is prevented by shoulder 19a of flange 19 abutting the face of panel 43, a feature contributing to the ease with which the tool may be withdrawn from the straight-through hole at the completion of the cut. The tool is normally used in this fashion as a conventional hole saw when it is desired t0 replace .the outer panel 43 with a new panel. The hole cut through the inner panel 42 provides a freshly cut well so that welding metal may be more easily applied from the inside of the panels.

Of course, the rotary cutting tool 10 is useful as an ordinary hole cutter in other applications, and in all applications, it eliminates the need for center punching due to the provision of the spring loaded pilot rod 24. yBy axially adjusting threaded plug 29, the tension of spring 28 can be set to produce heavy or light pressure ion pilot rod 24 for hole cutting in thick or thin metal respectively. Due to the provision of the centering pilot rod 24, tool l@ facilitates removal of spot welds which are located close to an edge of a panel where ordinary drills tend `to slip or skate off the panel. The pilot rod also permits overlapping cuts to be easily made with the tool when, for instance, the spot welds are located close together. Less metal is removed when the tubular saw type metal cutter 16 is used instead of a drill, thus hastening the disassembly of spot welded panels. Moreover, in the operation of the tool and in the method of the invention, the cutting occurs in the softest portion of the panels thereby contributing materially to the speed of the operation and the life of the tool. This is due to the fact that the metal in the area of the annular cut has been annealed by the heat generated during spot Welding, Whereas the surrounding metal remained in its work hardened state while that of the spot welded portion was rehardened by being subjected to more rapid cooling due t-o the presence of the water-cooled copper electrodes. In addition, by using the method of the invention, the panels are not nicked, bent or otherwise damaged as so often occurs when a chisel type tool is used to separate the panels,

I claim:

1. A method for separating two metallic members joined together by a spot Welded portion thereof, which cornprises removing metal from one of said metallic members in at least the portion thereof immediately surrounding said spot welded portion thereof to a depth at least equal to the thickness of said one member so that `only said spot welded portion of said one member remains connected to the other of said members as an integral projection on the surface thereof, thereby disconnecting said members without distorting the same and :with a minimum of metal being removed to efrect the disconnection.

2. A method for separating two metallic members joined together by a spot welded portion thereof, which comprises cutting an annular groove around said spot welded portion and through only one of said members so that only said spot welded portion of said one member remains connected to the other of said members as an integral projection on the surface thereof Within the `area surrounded by said groove, thereby disconnecting said members without distorting the same and with a minimum of metal being removed to effect the disconnection.

3. A method for disconnecting and rejoining two metallic members connected in a particular arrangement with one another by a spot welded portion thereof, including the steps of, removing metal from one of the members to form a groove around the periphery of the spot welded .portion thereof to a depth at least equal to the thickness `of said one member to thereby cut a hole therein so that said members are disconnected and so that the spot weld portion of said one member located Within the groove forms a projection on the surface of said other member, realigning said members in the original connected arrangement thereof by relocating said projection in said hole of said one member, and thereafter rejoining said members while retaining the members in the re-aligned arrangement.

4. The method as dened in claim 3 wherein said members are rejoined by welding said members to one another while retaining said members in the re-aligned arrangement.

5. A method for disconnecting and rejoining two metallic members connected in a particular arrangement with one another by a spot welded portion thereof, including the steps of, removing metal from one of the members to form a groove around the periphery of the spot welded portion there-of to a depth at least equal to the Ithickness of said one member to thereby cut a hole therein so that said members are disconnected and so that the spot weld portion of said one member located within the groove forms a projection on the surface of said other member, realigning said members in the original connected arrangement thereof by relocating said projection in said hole of said one member, temporarily holding said members together in the realigned arrangement, iand .applying low temperature welding metal into said groove formed between the sides of said hole in said one member and `the sides of said projection on said other member so that said members are rewelded together.

References Cited by the Examiner UNITED STATES PATENTS 1,900,682 `3 /33 Alcott 29-401 2,23 7,570 4/ 411 -Maillart 29-40t1 2,312,176 2/43 Kotowski 77-69 2,897,585 y8/59 `Bodewein 29-40'1 WHITMORE A. WLTZ, Primary Examiner.

'THOMAS H. `EAGER, Examiner. 

1. A METHOD FOR SEPARATING TWO METALLIC MEMBERS JOINED TOGETHER BY A SPOT WELDED PORTION THEREOF WHICH COMPRISES REMOVING METAL FROM ONE OF SAID METALLIC MEMBERS IN AT LEAST THE PORTION THEREOF IMMEDIATELY SURROUNDING SAID SPOT WELDED PORTION THEREOF TO A DEPTH AT LEAST EQUAL TO THE THICKNESS OF SAID ONE MEMBER SO THAT ONLY SAID SPOT WELDED PORTION OF SAID ONE MEMBER REMAINS CONNECTED TO THE OTHER OF SAID MEMBERS AS AN INTEGRAL PROJECTION ON THE SURFACE THEREOF, THEREBY DISCONNECTING SAID MEMBERS WITHOUT DISTORTING THE SAME AND WITH A MINIMUM OF METAL BEING REMOVED TO EFFECT THE DISCONNECTION. 